Patterns of diversity, connectivity, and evolution in Southern Ocean and deep-sea annelids

Abstract

The Southern Ocean surrounding Antarctica, and the deep oceans of the world more generally, are considered amongst the last remaining marine wildernesses on the planet. However, the remoteness that has protected these marine realms from direct anthropogenic impacts in the past have also made documenting their biodiversity challenging. As both direct and indirect anthropogenic threats increase, there is an urgent need to build an accurate baseline understanding of these ecosystems to evaluate threats, monitor change, and inform conservation efforts. Using benthic annelids as a model group, this thesis investigates biodiversity at various hierarchical levels in Southern Ocean and deep-sea habitats, from species to community level, local to regional, and comparing morphological, genetic, and genomic methods. A new species of deep-sea annelid, Neanthes goodayi sp. nov. is described from the abyssal central Pacific using both morphological and molecular data, highlighting polymetallic nodules (mineral resources targeted by potential seabed mining) as a unique microhabitat, in addition to the value of comprehensive integrative taxonomic description. The annelid community of a deep, previously ice-covered channel on the Antarctic Peninsula – the Prince Gustav Channel, is then documented using morphological-level identifications, giving first insights into the biodiversity of this previously unsampled channel, highlighting a functionally and spatially heterogeneous benthic community in a region already affected by climate change. DNA barcoding was then carried out for a subset of representative morphospecies from this dataset to investigate whether a barcode subsample improves morphological species identifications in relation to richness and diversity of the channel community, finding that, while overall biodiversity metrics were relatively unchanged, barcodes improved identification quality, and highlighted potential cryptic diversity. Finally, the first genomic level study of a Southern Ocean annelid using Single Nucleotide Polymorphism (SNP) data was carried out for the nephtyid Aglaophamus trissophyllus, using samples spanning much of the species’ distributional range across West Antarctica, revealing complex patterns of population structure and connectivity across the Southern Ocean, and finding support for potential cryptic lineages. Results of the thesis are synthesised and discussed in relation to the strengths, weaknesses and synergy of different methods for measuring Southern Ocean and deep-sea benthic biodiversity in the in the context of a global taxonomic impediment.

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Identifiers

ORCID for Regan Drennan: orcid.org/0000-0003-0137-5464

ORCID for Jon Copley: orcid.org/0000-0003-3333-4325

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